In many machines, the various movement sequences of the various machine parts also bring about unwanted vibrations. These unwanted vibrations can have a negative influence on the life of the machine or on user comfort, for example. Especially in powertrains constructed with internal combustion engines, a constant torque can generally not be introduced into a powertrain owing to the fact that periodic ignitions occur in the internal combustion engine and the energy that is released as a result is converted into a rotational movement of the crankshaft. The torque delivered by the crankshaft and also the rotational speed of the crankshaft are subject to fluctuations and oscillations, generally speaking, rotational irregularities. Since rotational irregularities of this kind may be noticeable during driving operation, it is desirable to eliminate them as far as possible.
For example, by employing force accumulators or energy accumulators, that is, for example, springs or moving masses, the energies occurring in rotational irregularities of the kind mentioned above are temporarily stored and are then conveyed into the powertrain in such a way that a smoother speed curve and/or torque curve can be achieved. However, systems of this type usually require extensive space.
Another possibility is to use phase shifter arrangements which, by initially splitting (power split) and then recombining the transmitted torque, can ensure that a destructive superposition of vibration components occurs in the torque to be transmitted as a result of the phase shift introduced. Ideally, a virtually complete elimination of rotational irregularities takes place at least in a particularly critical frequency range.
U.S. Pat. No. 8,991,531 shows a torsional vibration damping arrangement with two torque transmission paths, at least one of which has a phase shifter arrangement which generates a phase shift of rotational irregularities in the two torque transmission paths. The phase shifter arrangement is constructed substantially according to the working principle of a dual mass flywheel in which two masses, i.e., essentially the primary side and the secondary side, which oscillate with respect to one another against the action of the spring arrangement are provided with a desired vibration behavior through selection of the spring stiffness on the one hand and of the mass ratios and/or mass inertia at the primary side and secondary side on the other hand. A vibratory system of this type has a resonant frequency. In the frequency range below the resonant frequency, a vibratory system of this type vibrates subcritically, i.e., excitation and reaction of the system take place substantially simultaneously. When the resonant frequency is exceeded, a phase jump occurs so that excitation and reaction of the system occur substantially out of phase with one another, i.e., the system operates supercritically. This phase jump which ideally has a maximum value of 180° can be utilized to achieve the desired reduction of rotational irregularities in that the torque vibration component which has been phase-shifted in this way is superposed on the torque vibration component that has not been phase-shifted.
To further reduce rotational irregularities and in order to allow future requirements of automobile manufacturers to be met, systems with power capability appreciably superior to that of present-day systems are required. For example, the lower speed range is being focused on to an increasing extent because of increasing excitation, e.g., due to downspeeding (reduced engine speed) and/or downsizing (reduced engine displacement). In addition, there are new requirements, e.g., for engines with cylinder cutout, start/stop systems and/or different levels of hybridization, which cannot be mastered to a sufficient degree, if at all, with present-day concepts for reducing rotational irregularities.
Therefore, there is a need for providing a concept for torsional vibration damping which makes it possible to improve the reduction of rotational irregularities.